Input screen scintillator for a radiological image intensifier tube and a method of manufacturing such a scintillator

Abstract

The present invention provides an input screen scintillator for a radiological image intensifier tube in which the cesium iodide needles of the scintillator are coated with a refractory, transparent of reflecting, material having an optical index close to or less than that of the cesium iodide. Different methods may be used for coating, such as chemical vapor phase deposition, activated by thermal excitation, plasma excitation or photonic excitation; or such as diffusion deposition of a colloidal solution; or such as polymerization of a polymer resin. After coating, is realized the heat treatment which ensures the luminescence of the screen.

What is claimed is: 
     
       1. An input screen scintillator for a radiological image intensifier tube comprising a layer of juxtaposed cesium iodide needles having lateral sides extending transversally to said layer, said layer including gaps between the needles, wherein said needles are coated with a refractory material on their lateral sides within the gaps, and wherein said refractory material is transparent and has an optical refractive index approximately the same or less than that of said cesium iodide needles. 
     
     
       2. A method of manufacturing an input screen scintillator for a radiological image intensifier tube, comprising the steps of: forming a layer of juxtaposed cesium iodide needles having lateral sides extending transversally to said layer, said layer having gaps between the needles;   coating the lateral sides of the needles within the gaps with a transparent refractory material; wherein said refractory material has an optical refractive index approximately the same or less than that of said cesium iodide needles   and thereafter heat treating said input screen in order to insure the luminescence thereof.   
     
     
       3. The method of claim 2, wherein said transparent refractory material has an optical index approximately the same or less than that of the cesium iodide needles. 
     
     
       4. An input screen scintillator according to claim 1, wherein the material for coating the needles is an oxide of a metal or of a non metal. 
     
     
       5. An input screen scintillator according to claim 1, wherein the coating material is selected from the group consisting of SiO, SiO 2 , SiO x  with 1<x<2, Al 2  O 3 , Sb 2  O 5 , Si 3  N 4 , S n  O 4 . 
     
     
       6. The method of claim 2, wherein the step of coating the needles includes depositing said coating material by chemical vapor phase deposition. 
     
     
       7. The method of claim 2, wherein the step of coating the needles includes depositing said coating material by chemical vapor phase deposition, activated by thermal excitation, one of the following coating materials being used : SiO 2 , Si 3  N 4 . 
     
     
       8. The method of claim 2, wherein the step of coating needles includes depositing said coating material by chemical vapor phase deposition, activated by one of the following techniques : plasma excitation, photonic excitation, use of low pressure and high temperature. 
     
     
       9. The method of claim 2, wherein the step of coating the needles includes depositing said coating material by diffusion of a colloidal solution inside the gaps between needles, followed by heat treatment causing deposition of the coating material. 
     
     
       10. The method of claim 9, wherein said colloidal solution is selected from the group consisting of Si O 2 , Al 2  O 3 , Sb 2  O 5 , SnO 4 . 
     
     
       11. The method of claim 2, wherein the step of coating the needles includes having said cesium iodide needles coated in a vacuum with a polymer resin of the silicon type or any other polyimide material, and subsequent hardening of the coating material. 
     
     
       12. The method of claim 2, wherein the step of coating the needles includes having said cesium iodide needles coated by diffusion, between the needles, of an organo-metallic compound then undergoing one of the following treatments: high temperature, treatment air hydrolysis. 
     
     
       13. The method of claim 12, wherein said organo-metallic compound is selected from the group consisting of tetramethoxy-silane, tetra-ethoxy-silane, silicon tetra-acetate.